DXM+eyedrops?

I read on the DXM faq that DXM should not be combined with antihistamines. I'm using Opcon-A which says 'antihistamine' on the front, but its an eyedrop not a pill, will it affect me?

Also, why does the FAQ say this:
"SucretsTM (not the kind that come in the tin; these come in a bag and are labelled as containing DXM)."
I bought the kind in a plastic tin and all it says is "Medicinal ingredient: 15mg dextromethorphan hydrobromide"

They are talking about antihistamine pills, you'll be fine. If DXM is the only active ingridient, they're cool. Not sure what pills (or whatever) you have, but is DXM is all that is in them then party on. I'm trusting you to read a label correctly here, if you have any dought, don't take them.